Head for gas detectors



March 31, 1931.

A. N. ERICKSON HEAD FOR GAS DETECTORS Filed Deo. 5, 1927 2 Sheets-SheetFIGZ.

FIG. I.

FIG. 3.

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ATTORNEYS,

March 31, 1931. A, N ER|K50N 1,798,977

HEAD FOR GAS DETECTORS Filed Dec. 5, 1927 2 Sheets-Sheet 2 6 AT ToRNEYsPatented Mar. 31, 193,1

UNITED STATES PATENT OFFICE ALBERT N. ERICKSON, F ELMHU'RST, NEW YORK,ASSTGNOR T0 UNION CARBIDE COMPANY, A CORPORATION OF VIRGINIA HEAD FORGAS DETECTOLRS Application lerl December 5, 1927` Serial No. 237,971.

This invention relates to detectors for combustible gases and especiallyto means for providing an improved head for containing the resistanceelement thereof.

In my copending application, Ser. No. 181,- 227, filed April 5, 1927, Ihave disclosed an apparatus for detecting the presence of combustiblegases in an atmosphere. In this d`evice a iilament of a suitablematerial, such as platinum, is heated to such a temperature that if anycombustible gas be present in the atmosphere it will be oxidized. Thisoxidi- Zation causes a raising of the temperature of the filament andthis risein temperature is measured in any suitable manner, preferablyby noting the change in the resistance of the filament.

This invention has for its object the improvement of the head containingsuch a filament and especially the provision of means for making;r theinstrument more accurate.

.another object is to provide a head in which the current willautomatically be cut off from the filament When the protective bonnet isremoved.

These and other `objects of my invention will be evident from thefollowing specification having' reference to the accompanying drawingsin Which:

Figure 1 is a vertical cross section through. a detector headconstructed in accordance with my invention;

Figure 2 is aperspective view ofthe bonnet locking ring, the ring beinginverted to show the contacts carried thereby; y

Figure 3 is a perspective view of the filament cartridge supportingmember;

Figure d is a plan view of the top of the bonnet;

Figure 5` is a vertical cross section of another embodiment of. mydevice; and

Figure 6 is a section on line 6--6 of Figure 5. In my application,Serial No. 181,227', above referred to, I have disclosed an apparatus inWhich a. current of electricity is passed through a filament held in acartridge, the cartridge being of skeleton. form so that` the atmospheremay come into intimate @Qnact with the filament. The cartridge issecured in a head and surrounded by screens for the purpose ofpreventing `the propagation of the flame from the filament to thesurroumlingv atmosphere and further protected by a bonnet in order thatthe screen may not be accidently iiljured. The filament is heated tosuch a temperature that any combustible gases in the surroimding`atmosphere will be oxidized and the change in temperature of the.filament measured as disclosed in that appli cation. I prefer tomeasure this change in temperature by noting` ythe changeof resist# anceof filan'ient, this change in resistance being measured by any suitablemanner, such as by a Theatstone bridge.

In the apparatus shown in Figures 1 to 4 inclusive a detector head 10 ismounted on the staff 11. The head consists of a socket 12 and aprotective bonnet assembly 13. The bonnet assembly comprises anl outerbonnet 14, a plu-` rality of screens 15, said screens being` pro videdWith flanges at their base, and a lock` ing ring 17. This lockingr.ring` is provided with contact members 18 for a reason Which will` bemore fullysetforth herein. The socket 12 contains a cartridgesupportingmember 19 which `is made of insulating1 material.,` `Thiscartridge supporting member preferably made in the shape of a spool, theupper flange 21 being smaller in diameter than the lower 'liang'e 22,which carries two pairs of contacts 23, 24 and 25, 26 for engagementwith the contact pieces 18.` Theupper Hangs 21 carries a pair of posts2.7, 28, these posts being provided with projections 29 for holding; acartridge 31. A link 32 of nonconducting' material slides `on the posts27 and 28 forcing the ends together to grip the cartridge 31. y

`This form of my invention is assembled as follows: The socket 12 issecured to the staff 11 and a pair of conductors are led into the socketthrough a. hole 3.8 in they staff. One of these conductorsis connectedto the contact 23 and the other to the contact 26. The contact24 isconnected to the support 27 and the `contact 25 to the support 28through a centraiopening` ink the spool shaped supporting member. Thelocking ring' 17is then placed intoposition, the contact members 18passing lai through slots 33 in the upper flange 21. The ring is thenrotated 90o so that the members 18 close the circuit between contacts 23and 24 and between the contacts 25 and 26. The screen members 15 arethen placed in position above the locking ring 17 and the bonnet 14 isscrewed down, the interior threaded portion thereoil engaging` the outerthreaded portion 34 of the socket 12 and the outer threaded portion 35of the locking ring 17 Then the bot-tom of the bonnet 14 bears againstshoulder 36 on the socket 12, screws 37 are inserted through the bonnetand locking rings to hold these in fixed relation. Upon unscrewingthebonnetthe entire protective bonnet assembly, including the screensand locking` ring, is removed as a unit, the flange of the screens beinglocked between the locking ring and the shoulder on the inside oli thebonnet. The purpose of initially assembling the detector head in thismanner is to assure the engagement of the contacts 18 with the contactpieces 23, 24, 25 and 26 when the bonnet is screwed on. n

It will be seen that whenthe bonnet assembly is unscrewed to permit therenewal of the cartridge 31 containing the filament, the contacts 18 areseparated from the contact pieces 23, 24, 25 and 26 thus insuring thatthe heated filament is not exposed unprotected to the atmosphere. v Y

The cartridge 31 contains the filament which is heated to causeoxidation of the'combustible gas. This filament is preferably a platinumwire and I have found that a length of 11/2 inches of wire of a diameterof .O05 inches coiled on fg inch rod and stretched in a holder whoseends are 5/8 inches apart is very satisfactory. vWhile this cartridge orholder may be placed in any position I have found that for somecircumstances it is preferable to have the holderiairanged horizontally.This is especially true when it is desired that the detector heady shallpermit of tipping. If the holder be placed vertically and the headtipped the reading may be diminished by an amount corresponding` to asmuch as 0.75% of methane present in the atmosphere being tested. If theholder is arranged horizontally the head may be tipped, taking care tostill maintain the holder horizontally. In this case there will be nochange in the reading. Should the head be tipped in such a direction asto cause the holder to tend to assume a vertical position or should thehead, after being tipped with the holder horizontal, be rotated, therewill be a possibility of error but this wouldrshow a greater amount ofcombustible gas than is actually present.v

In order to insure that the holder is kept horizontal, the top of thebonnet is provided with a suitable marking 39 which bears a fixedrelation to the filament holder. While various forms of indiciamay'beused I have found a line parallel to the lilament holder to besatisfactory. This bonnet may be of any suitable material to protect thescreens and is provided with means whereby the at-mosphere may have freeaccess to the filament. A suitable construction for this bonnet isformed by cutting a series of short parallel slots in a cylinder ofbrass, aluminum or other suitable material and deformving the metalinwardly between pairs of adjacent slots as is clearly shown in Figure YIn Figures 5 and 6 I show another embodiment of my invention. Thisembodiment comprises a socket 41V and abonnet assembly 42, the bonnetassemblyconsisting of a bonnet 43, screen 44 and a locking ring 45. Thesocket contains posts 46 and 47 for holding a filament cartridgetherebetween, the post 46 being movable to permit of the replacement ofthe cartridge. In the socket are two curved slots 48 of T-shaped crosssection, these slots being provided with enlargements in the top portionthereof at Vone end as shown at 49. At the opposite end of the slots aremounted pairs of spaced contacts 51, 52 and`53, 54. One of the contacts,as 52, is connected to the post 46 and' one of the other pair, as 53, isconnected to the post 47. The other two contacts, 51 and 54, areconnected to the conductor'pair vwhich is led in through the hole 38 inthe staff 11. The bonnet carries a pair of studs 55. Each stud carriesan insulating washer. 56 which is L shaped in cross section. Mountedonthis washer is a 'contact making piece 57.

This form of my invention is assembled as follows.V The filament holderis secured between the posts 46 and 47 and the bonnet assembly issecured to the socket by causing the studs 55 ,to enter the enlargement49 in the slots 48. The bonnet assembly is then rotated 90 on thesocket, lockingV these together and closing the circuit between thecontacts 51, 52 andv v53, 54.

1. Ay head fora detector of combustible gases, comprising a baseforsupporting a resistor, Y an electrical circuit including said resistor,a protectivemember for said resistor and meanscarried by said protectivemember for closing said circuit.

2. A head for a detector for combustible gases comprising a base, meansfor supporting a resistor on saidY base, spaced contacts on said base, aprotective member surrounding said resistor and engaging said base andcontact pieces carriedA by said protectivev member for electricallyconnecting said contacts. 'p

3. head for a detectorfor combustible gases comprisingm'eans forsupporting a resistor, terminals on said supporting means electricallyconnectedto said resistor, terminals for an external circuitcarried by.said supporting means and a protective member `for said resistor. seidprotective means being provided With means for oompleting the circuitbetween said resistor ten minals and said external circuit terminals.

l. A. head for a detector of Combustible mises comprising a base7 meanson said base ior supportingr a resistor and a bonnet assembly. saidassembly comprising a proteotive bonnet, a plurality of screen membersWithin said bonnet and a locking ring, said bonnet assembly beingprovided With means for closing a. circuit to said resistor.

In testimony whereof, I aiix my signature.

ALBERT N. ERICKSON.

